The goal of this study was to identify clinicoradiologic characteristics to distinguish metastatic cancer to the pancreas (MCP) from double primary pancreatic cancer (DPPC).

From 2000 to 2011, we retrospectively identified MCP and DPPC patients among patients with histories of other primary malignancies.

A total of 94 patients with histories of other primary malignancies were histologically confirmed to have pancreatic cancer. Among them, 34 patients had MCP and 60 patients had DPPC, which were ductal adenocarcinomas. The kidney was the most common primary cancer site that metastasized to the pancreas (12, 35.3%). In the DPPC group, the stomach was the most common primary cancer site (11, 18.3%). There were 21 patients (61.8%) with metachronous pancreatic cancer in the MCP group and 29 (48.3%) in the DPPC group (P=0.210). Among the metachronous pancreatic cancer patients, the disease-free interval was 88.3months in the MCP group, and 49.6months in the DPPC group (P=0.062). The number of the patients who showed elevated CA 19-9 levels was higher in the DPPC group than in the MCP group (39 (65%) vs. 9 (26.5%); P=0.001). Total bilirubin (P=0.006) and fasting plasma glucose (P=0.050) were also higher in the DPPC group. The numbers of patients who showed pancreatic duct dilatation (P=0.002) and pancreatic atrophy (P=0.008) on radiographs were meaningfully higher in the DPPC group than in the MCP group. On the other hand, the numbers of patients who showed well demarcated tumor margin (P<0.000), tumor necrosis (P=0.002), enhancement (P=0.005) and distant metastasis (P=0.028) were significantly higher in the MCP group than in the DPPC group. We evaluated differences in survival between the two groups. The median survival time in the MCP group (55months) was significantly longer than that in the DPPC group (20months).

Other than elevated levels of CA 19-9, total bilirubin and fasting glucose, radiologic findings were the most reliable factors for distinguishing the MCP from the DPPC.